Large-tow fiber-placement system

ABSTRACT

A large-tow fiber placement system having (1) a creel, (2) a tow feeding mechanism, (3) a tow cutting mechanism, and (4) a tow consolidation system, wherein the creel shuttles a spool to maintain a substantially fixed exit path of a large-tow exiting the spool, the tow feeding mechanism has a head that is cooled by a fluid to control integrity of the large-tow and the tow consolidation system has interlocking shoes to provide a continuous application of the head is disclosed.

REFERENCE TO RELATED APPLICATION

This application claims priority to U.S. Provisional Application No. 60/640,235, filed Jan. 3, 2005, the contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The embodiments of the invention relate to a system for large-tow fiber placement. This invention transcends several scientific disciplines such as textiles, fibers, composites, mechanical engineering, materials science, and chemistry.

BACKGROUND

The term “large-tow” refer to tows having filaments ranging from 50K to 600K or more, for example 150K, which could be with or without pre-impregnated resin. Currently, the placement of large tow, particularly, resin pre-impregnated fibers, present a number of challenges in handling and application in the fiber-placement process. The subject invention embodies a practical process to apply large-tow, preferably pre-impregnated, fibers to surfaces through the use of specific tooling and process temperature controls.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: An embodiment of the shuttling-roller system.

FIG. 2: An embodiment of the tow tensioning assembly.

FIG. 3: An embodiment of the axial staggered mounting of the material spools.

FIG. 4: An embodiment of the towpreg feeding system.

FIG. 5: An embodiment showing the arrangement of the laser relative to the fiber band.

FIG. 6: An embodiment of the tow compaction system.

SUMMARY OF THE INVENTION

The embodiments of the invention relate to a large-tow fiber placement system comprising (1) a creel, (2) a tow feeding mechanism, (3) a tow cutting mechanism, and (4) a tow consolidation system, wherein the creel shuttles a spool to maintain a substantially fixed exit path of a large-tow exiting the spool, the tow feeding mechanism comprises a head that is cooled by a fluid, preferably a liquid, to control integrity of the large-tow and the tow consolidation system comprises interlocking shoes to provide a continuous application of the head. Preferably, the creel comprises a tow take-up mechanism to prevent slack of the large-tow. Preferably, the creel comprises staggered spindles to allow side-by-side alignment of a plurality of the large-tows. Preferably, the tow feeding mechanism comprises textured rollers. Preferably, the tow feeding mechanism comprises multiple rollers. Preferably, the feeding mechanism comprises a plurality of staggered cylinders to maintain a desired gap between a plurality of the large-tows. Preferably, the feeding mechanism is self-threading. Preferably, the feeding mechanism comprises a modular side-drive assembly to allow for an ease of maintenance. Preferably, the tow cutting mechanism comprises a laser. Preferably, the laser is mounted in a fixed position with the beam being directed to the large-tow through telescoping optics. Preferably, a shuttling head allows the laser to cut one or more large-tows from a plurality of large-tows. Preferably, the laser is contained beyond the large-tow with a monolithic carbon trap. Preferably, the tow consolidation system further comprises a wiper-blade to provide smooth spreading and consolidation of the large-tow. Preferably, the tow consolidation system pulls the large-tow straight onto an application surface. Preferably, the tow consolidation system prevents overlap of a plurality of the large-tows on an application surface. Preferably, the tow consolidation system eliminates the generation of catenaries at an application point of an application surface. Preferably, the tow consolidation system further comprises compaction cylinders and the interlocking shoes are mounted on the ends of the compaction cylinders. Preferably, the interlocking shoes have a tangential swiveling capability. Preferably, the wiper blade has a continuous, unbroken surface to contact a plurality of the large-tows.

As will be realized, this invention is capable of other and different embodiments, and its details are capable of modifications in various obvious respects, all without departing from this invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION

As used in the specification and claims, the singular forms “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. The embodiments of the invention relate to the following components of the large-tow fiber placement system.

Creel: In the preferred embodiments, the creel has the following features: (1) Axially shuttles a spool to maintain a fixed towpreg centerline exit path. (2) Ablity to utilize large material spools to minimize material change-outs. (3) Uses a lightweight roller for payoff position feedback. (4) Tow take-up mechanisms (individually and/or collectively) to prevent tow-slack in the system. (5) Staggering of material spindles to allow side-by-side tow alignment.

Tow Feed and Cut Mechanism: In the preferred embodiments, the tow feed and cut mechanism has the following features: (1) Textured rollers to provide superior tow pull. (2) Use of multiple rollers to maximize feed pull-force. (3) Staggering (fore and aft) of cylinders to minimize gap between tows. (4) Liquid cooling of head to provide accurate cooling to control tow integrity. (5) Design has self-threading feature. (6) Modular side drive assembly design to allow for the ease of maintenance. (7) Cutting or terminating of the tow feed could be done with an industrial laser as required “on the fly”.

Tow Consolidation System: In the preferred embodiments, the tow consolidation system has the following features: (1) Individual interlocking shoes to provide a continuous but compliant application head. The interlocking shoes could also swivel to provide a continuous consolidation force that conforms to application surface. (2) A wiper-blade applicator to provide smooth spreading and consolidation of tows. (3) Pulls tows straight onto the application surface. (4) Prevents tow overlap on application surface. (5) Eliminates the generation of catenaries at the application point. (6) Single application-plane delivery.

The subject invention has been demonstrated to provide a means to economically apply a wide band of large-tow, resin pre-impregnated fiber to a surface to create a high strength, lightweight, structure. The embodiments of the invention satisfy a great need for such equipment and processes in the energy, and transportation industries. Examples of applications include manufacturing large wind turbine blades, aircraft and automotive panels, etc.

EXAMPLES

Creel

In order to achieve manufacturing efficiency, the subject machine could use towpreg and spools significantly larger than those traditionally used. The spools typically used, for example, are around 35 inches in length and, when loaded with material, weigh approximately 90 lbs. The creel of the embodiments of the invention could use spools of other sizes and weights. Grooved rollers could be used to direct and route the tows into the machine.

In order to maintain capture of the tows by guide rollers, it is preferable that each tow feed off of their respective spools substantially straight into a guided path. This is accomplished by shuttling the material spool back and forth to keep the payoff point aligned with the centerline of the appropriate guide roller. A system was created using low-cost components, which minimizes the amount of processing power required in closed-loop control. This system was accomplished by a novel design of the shuttling rollers—the first grooved roller the tows encounter as they leave their spool. The shuttling roller is free to rotate about a shaft as well as translate side to side. As each tow pays off its respective spool, the pay off point moves axially with respect to the spool. As it does so, the tow drags the shuttling roller along with it axially. The axial movement of the shuttling roller is constrained by blocks placed approximately 4 inches apart on the roller shaft with the shuttling roller between these two ‘set-point’ blocks. A proximity sensor is mounted on each of the two limiting blocks and interacts with the shuttling roller. As the shuttling roller reaches the maximum allowed travel defined by the position of a set-point block, a signal is produced by the respective proximity sensor. This signal is noted by a controller that then opens a valve supplying air to a pneumatic cylinder. The pneumatic cylinder moves the towpreg spool in the proper direction to re-position the payout point with the nominal centerline. As it does so, the shuttling roller is dragged along with it and the sensor signal is restored, the air to the pneumatic cylinder is stopped, as is the movement of the towpreg spool. The towpreg spool again remains axially stationary until the payout point has once again dragged the shuttling spool to its set-point where the closed-loop process begins again. This process continues until the towpreg wrapping turn-around point is reached at which time the unwinding of the towpreg drags to shuttling roller to the opposing set-point block which then initiates a movement of the towpreg spool in the opposite direction.

The operation of this system provides the ability of the shuttling roller to move easily and freely. This is accomplished through the use of very low friction bearings and the design of the shuttling roller itself to be lightweight. Each roller has a lead-in into its containment groove to insure that the tow is and remains captured. Axial dragging of the shuttling roller is created because of relatively high, straight walls on the sides of the groove. The shuttling-roller system is illustrated in FIG. 1.

In order to prevent the tows from jumping out of the grooves of the roller they pass over, and to prevent the tows from tangling with each other, a slight tension needs to be maintained in each tow. This is accomplished by two unique systems. The first system uses springs and pneumatic cylinders to interact with each tow individually. As the payout rate on each tow varies, an individual pneumatic cylinder extends or retracts to take up the desired slack and maintain the desired tension. Large excursions are handled by the springs.

The other take-up system is used to take up slack created by vertical movements of the head when tows are not being paid out. The system uses linear actuators slaved to the vertical movement of the head to take up slack in all the tows simultaneously. At the end of a lay-down pass the head must be raised to position it for the start of another pass. When this occurs, the above-mentioned actuators extend a roller to take up the resulting slack in the tows. At the beginning of the lay-down pass the head is lowered to contact the mandrel surface. At this time the actuators retract the roller and allow the tows to pay out. The actuators use the lay-down rate to determine the retraction rate of the roller to assure that no slack in introduced into the tows and allows the roller to be completely retracted and ready for another cycle. The tow tensioning assembly is shown in FIG. 2:

Another design feature of the creel is the axial staggering of the material spool mounting. This allows side-by-side placement of the tows as they feed into the fiber placement head. The axial staggered mounting of the material spools is illustrated in FIG. 3.

Tow-Feed Mechanism

To start the towpreg lay-down process, the tows should preferably be advanced to a nip point and back tension must be relieved to facilitate the band start. Both of these functions are accomplished by a tow-feeding mechanism that incorporates several unique features.

Textured rollers are used to grip and feed the tows. This type of roller provides a superior feeding force when compared to simple rubber or coated rollers. Multiple rollers are used to further increase the feeding force.

Another unique feature of this design is the fore and aft staggering of the pneumatic cylinders used to pinch the tows against the textured rollers. Because the tows on this design are on a single plane (the same principle works with a staggered plane delivery), it is desired to minimize the gap between the tows. In order to provide maximum pull force it is desired to use the largest pneumatic cylinders and pinch rollers possible. This is accomplished by staggering the pneumatic cylinders.

In order to prevent sticking of the towpreg to components, it is desired to cool the tows so that they are not tacky. One way the cooling could be accomplished is through the use of cooled gases. Another way the cooling could be accomplished is by using a liquid coolant to control the temperature of surfaces in contact with the tow.

The tow-feed mechanism incorporates a self-threading feature to minimize the time required to set up the head. Tows can be introduced at the back of the head and they are automatically fed through the head to the nip point.

To facilitate maintenance, this design allows some or all pinch rollers to be removed from the top and all textured rollers to be removed from the side. The towpreg feeding mechanism is shown in FIG. 4.

Tow-Cutting Mechanism

Tow-cutting is done with a laser during the fiber placement process. An industrial power laser generator is mounted in a fixed position with the laser beam being directed to location through telescoping optics. A shuttling right angle head allows the common laser to cut tows individually anywhere across the full bandwidth. The focal point of the laser power is optically focused to be at the point where it crosses the fiber path. Laser power is sufficient to cut through a large tow such as 150K “on the fly” during the fiber placement process. The laser beam beyond the fiber tow is contained with a monolithic carbon trap. The laser beam trap is cooled by a liquid cooled platen upon which it is mounted. FIG. 5 shows the arrangement of the laser relative to the fiber band.

Tow Consolidation System

To ensure that the tows stay in place in the laminate, and to eliminate voids, a compaction or consolidation system must be used. The tow consolidation system for this design uses pneumatic cylinders to provide the compaction force. Use of pneumatic cylinders assures that the compaction force remains constant, as long as the stroke of the cylinders is within their limits.

Compaction shoes are mounted on the ends of the compaction cylinders. These shoes form a single tier and feature a unique interlocking design to eliminate any across-the-bandwidth gaps in compaction elements. This feature, along with the shoes tangential swiveling capability, and position changes made possible by the pneumatic cylinders, accommodates a varying-radius crowned application surface.

Another unique feature of the compaction system is the use of a wiper blade placed under the compaction shoes. This blade is made of a low-friction, long-wearing material and is the element that actually comes in contact with the towpreg. The use of a sliding rather than a rolling element provides superior spreading capability, smoothness of the laminate, and pulls the tows straight in the lay-down process. The wiper blade also prevents tow overlap and a band of fibers free of catenaries (loose fibers that stick to and can roll up on rotating elements). The wiper blade presents a continuous, unbroken surface to the towpreg so there are no cracks or crevasses to catch or snag fibers during application. This makes for a self-cleaning and highly reliable system. The wiper blade tends to smooth out the distribution of the compaction force and protects the compaction shoes from wear.

While the wiper blade is preformed to a desired mid-range radius, it is compliant enough to allow conformance to other radii. The wiper blade can be fabricated to help guide the tows to their proper positions. The tow compaction system is shown in FIG. 6. 

1. A large-tow fiber placement system comprising (1) a creel, (2) a tow feeding mechanism, (3) a tow cutting mechanism, and (4) a tow consolidation system, wherein the creel shuttles a spool to maintain a substantially fixed exit path of a large-tow exiting the spool, the tow feeding mechanism comprises a head that is cooled by a fluid to control integrity of the large-tow and the tow consolidation system comprises interlocking shoes to provide a continuous application of the head.
 2. The large-tow fiber placement system of claim 1, wherein the creel comprises a tow take-up mechanism to prevent slack of the large-tow.
 3. The large-tow fiber placement system of claim 1, wherein the creel comprises staggered spindles to allow side-by-side alignment of a plurality of the large-tows.
 4. The large-tow fiber placement system of claim 1, wherein the tow feeding mechanism comprises textured rollers.
 5. The large-tow fiber placement system of claim 1, wherein the tow feeding mechanism comprises multiple rollers.
 6. The large-tow fiber placement system of claim 1, wherein the feeding mechanism comprises a plurality of staggered cylinders to maintain a desired gap between a plurality of the large-tows.
 7. The large-tow fiber placement system of claim 1, wherein the feeding mechanism is self-threading.
 8. The large-tow fiber placement system of claim 1, wherein the feeding mechanism comprises a modular side-drive assembly to allow for an ease of maintenance.
 9. The large-tow fiber placement system of claim 1, wherein the tow cutting mechanism comprises a laser.
 10. The large-tow fiber placement system of claim 9, wherein the laser is mounted in a fixed position with the beam being directed to the large-tow through telescoping optics.
 11. The large-tow fiber placement system of claim 10, wherein a shuttling head allows the laser to cut one or more large-tows from a plurality of large-tows.
 12. The large-tow fiber placement system of claim 10, wherein the laser is contained beyond the large-tow with a monolithic carbon trap.
 13. The large-tow fiber placement system of claim 1, wherein the tow consolidation system further comprises a wiper-blade to provide smooth spreading and consolidation of the large-tow.
 14. The large-tow fiber placement system of claim 1, wherein the tow consolidation system pulls the large-tow straight onto an application surface.
 15. The large-tow fiber placement system of claim 1, wherein the tow consolidation system prevents overlap of a plurality of the large-tows on an application surface.
 16. The large-tow fiber placement system of claim 1, wherein the tow consolidation system eliminates the generation of catenaries at an application point of an application surface.
 17. The large-tow fiber placement system of claim 1, wherein the tow consolidation system further comprises compaction cylinders and the interlocking shoes are mounted on the ends of the compaction cylinders.
 18. The large-tow fiber placement system of claim 1, wherein the interlocking shoes have a tangential swiveling capability.
 19. The large-tow fiber placement system of claim 1, wherein the fluid is a liquid.
 20. The large-tow fiber placement system of claim 13, wherein the wiper blade has a continuous, unbroken surface to contact a plurality of the large-tows. 